Incorrect age in the test results

I have a matrix with many cases who generate some JUnit reports. These reports are read by the performance plugin.

When I go in the Test Results page, there is an age column. The ages in this column are not correct and change sometimes with no reason.

For example, the build 26616 contain a test who fail for the past 164 builds. But Jenkins don't always says that. Sometimes it says that the age is 26617.

When I have the problem, I should follow the "Previous Build" links to come back to first failure of the test. And then when I click on "Next Build", the age is the good one.